linux-kernel - Re: [PATCH v11 1/2] irqchip: gicv2m: Add support for ARM GICv2m MSI(-X) doorbell

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Date:	Wed, 26 Nov 2014 11:25:44 +0000
From:	Marc Zyngier <marc.zyngier@....com>
To:	Mark Rutland <mark.rutland@....com>
CC:	Thomas Gleixner <tglx@...utronix.de>,
	Jason Cooper <jason@...edaemon.net>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"suravee.suthikulpanit@....com" <suravee.suthikulpanit@....com>,
	Jiang Liu <jiang.liu@...ux.intel.com>,
	Yingjoe Chen <yingjoe.chen@...iatek.com>
Subject: Re: [PATCH v11 1/2] irqchip: gicv2m: Add support for ARM GICv2m MSI(-X)
 doorbell

Hi Mark,

On 26/11/14 11:11, Mark Rutland wrote:
> Hi Marc,
> 
> On Tue, Nov 25, 2014 at 06:47:22PM +0000, Marc Zyngier wrote:
>> From: Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
>>
>> ARM GICv2m specification extends GICv2 to support MSI(-X) with
>> a new register frame. This allows a GICv2 based system to support
>> MSI with minimal changes.
>>
>> Signed-off-by: Suravee Suthikulpanit <Suravee.Suthikulpanit@....com>
>> [maz: converted the driver to use stacked irq domains,
>>       updated changelog]
>> Signed-off-by: Marc Zyngier <marc.zyngier@....com>
>> ---
>>  arch/arm64/Kconfig              |   1 +
>>  drivers/irqchip/Kconfig         |   6 +
>>  drivers/irqchip/Makefile        |   1 +
>>  drivers/irqchip/irq-gic-v2m.c   | 333 ++++++++++++++++++++++++++++++++++++++++
>>  drivers/irqchip/irq-gic.c       |   4 +
>>  include/linux/irqchip/arm-gic.h |   2 +
>>  6 files changed, 347 insertions(+)
>>  create mode 100644 drivers/irqchip/irq-gic-v2m.c
> 
> [...]
> 
>> +static int gicv2m_irq_domain_alloc(struct irq_domain *domain, unsigned int virq,
>> +				   unsigned int nr_irqs, void *args)
>> +{
>> +	struct v2m_data *v2m = domain->host_data;
>> +	int hwirq, offset, err = 0;
>> +
>> +	spin_lock(&v2m->msi_cnt_lock);
>> +	offset = find_first_zero_bit(v2m->bm, v2m->nr_spis);
>> +	if (offset < v2m->nr_spis)
>> +		__set_bit(offset, v2m->bm);
>> +	else
>> +		err = -ENOSPC;
>> +	spin_unlock(&v2m->msi_cnt_lock);
>> +
>> +	if (err)
>> +		return err;
>> +
>> +	hwirq = v2m->spi_start + offset;
>> +
>> +	err = gicv2m_irq_gic_domain_alloc(domain, virq, hwirq);
>> +	if (err) {
>> +		gicv2m_unalloc_msi(v2m, hwirq);
>> +		return err;
>> +	}
>> +
>> +	irq_domain_set_hwirq_and_chip(domain, virq, hwirq,
>> +				      &gicv2m_irq_chip, v2m);
>> +
>> +	return 0;
>> +}
>> +
>> +static void gicv2m_irq_domain_free(struct irq_domain *domain,
>> +				   unsigned int virq, unsigned int nr_irqs)
>> +{
>> +	struct irq_data *d = irq_domain_get_irq_data(domain, virq);
>> +	struct v2m_data *v2m = irq_data_get_irq_chip_data(d);
>> +
>> +	BUG_ON(nr_irqs != 1);
> 
> We didn't check nr_irqs at all in gicv2m_irq_domain_alloc, which seems a
> bit odd given this BUG_ON.
> 
> Is the caller responsible for checking we only allocated one irq, or is
> it only valid to ask for one?

We already have a strong guarantee from the alloc path that we'll never
see nr_irqs != 1, as we don't support MULTI_MSI just yet.

This BUG_ON() is more a debug leftover.

>> +	gicv2m_unalloc_msi(v2m, d->hwirq);
>> +	irq_domain_free_irqs_parent(domain, virq, nr_irqs);
>> +}
>> +
>> +static const struct irq_domain_ops gicv2m_domain_ops = {
>> +	.alloc			= gicv2m_irq_domain_alloc,
>> +	.free			= gicv2m_irq_domain_free,
>> +};
>> +
>> +static bool is_msi_spi_valid(u32 base, u32 num)
>> +{
>> +	if (base < V2M_MIN_SPI) {
>> +		pr_err("Invalid MSI base SPI (base:%u)\n", base);
>> +		return false;
>> +	}
>> +
>> +	if ((num == 0) || (base + num > V2M_MAX_SPI)) {
>> +		pr_err("Number of SPIs (%u) exceed maximum (%u)\n",
>> +		       num, V2M_MAX_SPI - V2M_MIN_SPI + 1);
> 
> That warning is a bit odd for the num == 0 case. Perhaps
> s/exceed/invalid,/ ?

Sure.

>> +		return false;
>> +	}
>> +
>> +	return true;
>> +}
>> +
> 
> [...]
> 
>> +static int __init gicv2m_init_one(struct device_node *node,
>> +				  struct irq_domain *parent)
>> +{
>> +	int ret;
>> +	struct v2m_data *v2m;
>> +
>> +	v2m = kzalloc(sizeof(struct v2m_data), GFP_KERNEL);
> 
> Minor nit: sizeof(*v2m) would be preferable.
> 
>> +	if (!v2m) {
>> +		pr_err("Failed to allocate struct v2m_data.\n");
>> +		return -ENOMEM;
>> +	}
>> +
>> +	ret = of_address_to_resource(node, 0, &v2m->res);
>> +	if (ret) {
>> +		pr_err("Failed to allocate v2m resource.\n");
>> +		goto err_free_v2m;
>> +	}
>> +
>> +	v2m->base = ioremap(v2m->res.start, resource_size(&v2m->res));
>> +	if (!v2m->base) {
>> +		pr_err("Failed to map GICv2m resource\n");
>> +		ret = -ENOMEM;
>> +		goto err_free_v2m;
>> +	}
>> +
>> +	if (!of_property_read_u32(node, "arm,msi-base-spi", &v2m->spi_start) &&
>> +	    !of_property_read_u32(node, "arm,msi-num-spis", &v2m->nr_spis)) {
>> +		pr_info("Overriding V2M MSI_TYPER (base:%u, num:%u)\n",
>> +			v2m->spi_start, v2m->nr_spis);
> 
> It would be nice if we could warn if only one of these properties is
> present.

Yup. I'll tighten that in an additional patch, as Jason has already
queued this.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...
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